Acid inhibitor



252. COMPOSITIONS.

(A; Patented Nov. 26, 19437 UNITED STATES PATENT OFFICE ACID INHIBITOR No Drawing.

Application April 18, 1938,

Serial No. 202,734

8 Claims.

This invention relates to the inhibition of the action of acids upon metals. Moreover in certain processes such as cleaning and pickling metals by employment of acids the use of this novel inhibitor as an addition reagent, permits the acid to act upon the corrosion products as rust and scale without attacking the metal itself except to a very minor extent. This invention is not in any sense limited to pickling operations but finds utility wherever an acid is brought in contact with metal such as in the transportation of acids or in oil drilling operations and wherein it is important that the action of said acid upon the metal or metals in contact therewith be reduced to a minimum. The invention has as one of its objects the preparation of the novel products.

It has been stated by Gravell in U. S. Patent #1,678,776 that it has been proposed to control the action of the pickling bath by such organic substances as: anthracene residues, oil sludge tar, gelatine, glue, pine oil, alcohols, yellow oil from the manufacture of butyl alcohol, resins and formaldehyde; but as Gravell points out on page 1, lines 76-85 there are certain objectionable eiiects. It has been proposed by Vogel in U. S. Patent #1,433,579 to pickle iron with acids as dilute mineral acids containing added substances as (A) anthracene, the waste lyes from the sulfite cellulose manufacture (B) the extract of these substances produced by treatment with inorganic acids, neutral or acid salts, organic solvents as hydrocarbons. Fontainemoreau in British Patent #10,6'79 of 1845 enumerates as one of several materials, to deter the action of acids on metals, the products of the dry distillation of organic substances such as the product of the. distillation of wood, coalifici Recently a French acids from. the distillatioznonnardmodlmth anhydrous NHa, aqueQw-w pifijdnmonium carbonate," ammonium acetate, or any su'itable ammonia salt or mixtures of same. For a clearer understanding of the material which is treated it seems best to give a resume of the steps for producing the same.

In the distillation of hardwood the condensable portion of the distillate is known as pyroligneous acid or pyroligneous liquor. This liquor may be allowed to stand whereupon a tar, known as settled tar, settles out and is removed; then upon evaporation of the clear pyroligneous acid a tar is left which was soluble in the pyroligneous acid, and known as soluble tar. Or the liquor may be conducted directly to a still and the soluble" tar and settled tar left together as a residue. In any event the tar is first stripped of water and acetic acid which it contains and is then subjected to distillation. This distillation may be conducted at atmospheric pressure Pyroligneous liquor y oligneous acid Settled I I I Acetic Higher Crude AlcohoY Soluble acid boiliing methanol oils tar aci s Aqueous Light Hez wy lilard wood distillate oils oils pitch All of the oils contain some tar acids and "tar bases these names being used to denote. the caustic soluble and acid soluble portion, respectively. Furthermore, the percent of a given sample of oil that is soluble in an acid of deflnite concentration at a specified temperature is a definite, reproduceable amount. 'I'hisis well known to the art.

In one embodiment as mentioned above, wood oil is reacted with NH: or compounds thereof. The reacted product, after the removal of the water, can be removed from the unreacted oil by extracting with sulfuric or hydrochloric acid or by distillation or by other means now known to the art. If extracted with sulfuric or hydrochloric acid this extract may be used as an inhibitor or the solution neutralized by any alkali or alkali metal salt whereupon the product will separate.

Examize,

dWA MJ- l/ While I have described certain wood oils which may be employed in carrying out my invention, it will be understood that there are other wood oils which I may use. In the claims, when I use 5 the term "wood oil, I mean any oil derived from the distillation of hardwood and comprising any portion that will react with ammonia. I prefer to use the-oil containing the most of this reactive ingredient, naturally, and in the examples which follow I will use the light oil fraction mentioned above.

It seems likely that the products formed in carrying out my invention are first ammonium salts of the reactive organic compounds which then undergo further change to yield organic nitrogen compounds. However, I do not fully understand the nature of the reactions involved and do not wish to be bound by the above theoretical explanation. It is sufficient that a reaction does take place which yields a novel product and the presence of NH NI-I2 or substituted products of same in the inhibitor is suflicient proof of the reaction.

The 'nature of my novel inhibitor and the processes of its manufacture and use may be more clearly understood from the following examples:

Example I 1,000 pounds of light oil are charged into a reaction tank and 60 pounds of ammonium carbonate added. The charge is agitated and the reaction allowed to proceed at room temperature as long as gas is evolved. The charge is then 85 heated to the boiling point by means of steam coils in the tank to bring the reaction to completion. The water formed as a product of the reaction is drawn off the bottom of the tank. The oil is then allowed to cool and charged into an agitator tank. Forty gallons of 22 hydrochloric acid are added and the charge agitated for one hour with a mechanical agitator. It is not usually necessary to heat the charge but may be necessary to cease the agitation temporarily to 5 keep the charge from becoming excessively heated. I prefer to allow the temperature to reach 65 C. during the agitation. After agitating the charge is allowed to settle for two hours and the inhibitor in hydrochloric acid solution is drawn oil from the bottom.

This solution is soluble in sulfuric acid or hydrochloric acid and is a superior inhibitor when added to acids which contact metals such as in pickling baths, etc.

Example I] 1,000 pounds of light oil are charged into an agitator tank. Gaseous NH: is bubbled through the charge until the reaction ceases. The temperature will rise rapidly then when sumcient NI-Ia has been introduced will start to fall. After settling the water formed during the reaction is withdrawn and 40 gallons of 20 hydrochloric acid are added to the oil in tank. This is agi- 65 tated for one hour, settled and the solution of inhibitor withdrawn.

Example 11! 2,000 pounds of light oil are subjected to frac- 70 tional distillation and the fraction boiling between 110 C and 200 C. at atmospheric pressure is placed in the agitating tank. 35 pounds of ammonium carbonate and 40 pounds of ammonium hydroxide are added. This charge is 75 agitated until cool, then allowed to settle and the water layer drawn off. 40 gallons of 18 B. hydrochloric acid are added, the charge agitated. After settling the inhibitor in solution is drawn off.

The efficiency of this inhibitor was tested as 5 follows:

Strips of mild steel /2" x 2" x 16 ga. were freed of scale, carefuly cleaned, and weighed. These were then immersed in acid solution for the time and at the temperature indicated in the table. 10 The percentages of inhibitor are given as percent by weight based on the weight of 18 B. hydrochloric acid in the solutions.

15 Temp. Metal Percent Time, Percent Amd inhibitor g f min. ig efliciency 18 B. hydrochloric 180 15 l. 4500 From the examples it is evident that a wide variation of time and temperature conditio possible in the operation of my novel processes without departing from the scope of my invegn; tion. The ultimate temperature attained must, be high enough to permit the reaction toproceed j properly, and not so high as to result in thernial decomposition or excessive polymerization ol tlf fe product. The rate at which this ultimate tem perature is reached may also be widely varied as without materially altering the results obtained.

It is well known that there are many acids in pyroligneous acid besides acetic acid. In the refini-ng of acetic acid it is customary to remove most, or all of the other acids at some state in the process. The recovery of acetic acid from the crude pyroligneous acid may be accomplished by different methods. The pyroligneous acid may be demethanolized, then the acetic acid recovered from the demethanolized liquor by scrubbing, azeotropic distillation, extraction and other means now known to the art, or the pyroligneous acid may be distilled and the acetic acid removed from the vapors by scrubbing before demethanolizing. In any event in the refining of acetic acid the higher boiling acids are eliminated. These are known by the names of hiboiling acid, crude brown acid, crude propionic acid and others. They are composed mainly of various concentrations of propionic acid, acetic I 5 acid and oil impurities. In the examples I will designate this product as crude higher boiling acids.

In the second embodiment of this present invention as pointed out supra crude higher boil- 00 ing acids obtained from the distillation of hardwoods are reacted with ammonia or salts of ammonia or combinations of same.

It seems likely that the products formed in this second embodiment are first the ammonium salts of the acids present which then react with some of the oily constituents to yield the novel product. However, I do not fully understand the nature of the reactions involved and do not wish to be bound by the above theoretical explanation. It is sufiicient that a reaction does take place which yields a novel product and the pressure of NH NI-Iz or other substituted products of nitrogen in the inhibitor is sumcient proof of the reaction.

The nature of my novel invention and the 252. COMPOSITIONS.

processes of its manufacture and use may be more clearly understood from the following examples:

Example IV gallons of crude higher boiling acids are charged into a reaction vessel equipped with cooling coils. 20 gallons of ammonia 26 B. are slowly added, with agitation, and the temperature of the mixture not allowed to exceed 50 C. This mixture is entirely soluble in acids and is an excellent inhibitor.

Example IV 100 gallons of crude higher boiling acids are charged into a reaction vessel equipped with cooling coils. Ammonia is added slowly, keeping the temperature below 50 C. until all the acids in the charge are neutralized. The inhibitor will separate and is drawn oil from the bottom. The ammonium salts of the acids which had not reacted with the oil to produce an inhibitor may be recovered from the water layer if desired.

Example V 100 gallons of crude higher boiling acids are charged into a reaction vessel. pounds of ammonium carbonate are added and the reaction allowed to proceed to completion. The charge which has present some acids may then be neutralized with sodium hydroxide being careful to keep the temperature below 50 C. The inhibitor will settle to the bottom and may be drawn on. The sodium salts of the acids which had not reacted with the oil to produce an inhibitor may be recovered from the water layer if desired.

The efliciency of this inhibitor was tested as follows: Strips of mild steel x 2" x 16 ga. were freed of scale, carefully cleaned and weighed. These were then immersed in acid solution for the time and at the temperature indicated in the table. The percentages of inhibitor are given as percent by weight based on the weight of 18 B. hydrochloric acid in the solution.

Temp. Metal Percent 'lime, Percent Add inhibitor l min. fg efliciency 18 Be. hydrochloric. 0 15 1.3125 2 180 15 0.0204 98.4 1 180 15 0.0212 91.9 0.5 180 15 0.0428 96.7 0 120 60 0.2505 1 120 00 0.0044 98.3 0.5 120 60 0.0124 95.2 0.25 120 00 0.0100 93.8

From the examples it is evident that a wide variety of concentration of the reactants is possible in the operation of my novel process without departing from the scope of my invention. The ultimate temperature attained may also vary over quite a range. In fact it is evident that it will be necessary to vary the proportion of reactants depending on the composition of the crude higher boiling acids, which will not only vary from different sources and methods of refining but will vary from time to time from a given source. Of course the crude acetic acid could be employed, since it contains these higher boiling acids and reactive impurities. But since the proportion of these reactive impurities is less in the crude acetic acid than in the crude higher boiling acids fraction, it is not so feasible. This less concentrated source of the active ingredient or ingredients is therefore more of an academic interest in comparison; but it is of course an available source. Likewise other modes of fractionation resulting in a higher concentration of these reactive impurities than in the conventional crude higher boiling acids fractionation will give a product which is very suitable for the production of my novel product. The essential thing is the presence of material often referred to as oil impurities, which is present with the acids.

It seems most likely that the active ingredient of the first embodiment and the second embodiment of this invention are the same; however, I do not fully understand the nature of the reactions involved and do not wish to be bound to any theoretical explanation. It is sufficient that a reaction does take place which yields a novel product and the presence of substituted products of nitrogen in the inhibitor is suificient proof of the reaction.

It is to be understood that I do not limit myself to the foregoing examples or descriptions except as indicated in the following patent claims.

I claim:

1. In the process for the manufacture of organic nitrogen derivatives of wood oils produced from the distillation of hardwood, the step comprising: reacting wood oils at a temperature below the range of thermal decomposition of the product with a substance which has available NHs and in whose structural formula none of the H atoms of the NI'I! are replaced.

2. As a new composition of matter the products formed by the reaction of claim 1.

3. As a new composition of matter the products obtainable in accordance with the process set forth in claim 6.

4. A mineral acid solution containing therein a relatively small amount of a metal corrosion inhibitor comprising the reaction product of claim 1.

5. A cleaning and pickling bath for metals comprising a solution of a mineral acid and a relatively small amount of a corrosion inhibitor comprising the reaction product of claim 1.

6. In the process for the manufacture of organic nitrogen derivatives of wood oils produced from the distillation of hardwood, the steps comprising: reacting wood oils at a temperature below the range of thermal decomposition of the product with a substance which has available NHs, in whose structural formula none of the H atoms of the NI-h are replaced, removing the water formed in the reaction and freeing the reaction product from the unreacted oil. 

